AIRCRAFT MAINTENANCE
Continuing analysis and surveillance system (CASS)
Reliability & Safety
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Reliability
Definition
 “The probability that an item will perform a required
function, under specified conditions without failure, for a
specified amount of time.”
2 Main Approaches
 Looks at Whole Operation : Dispatch Reliability
 Looks at Maintenance Program : Reliability Program
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Reliability
Term Reliability
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Overall Reliability
Component Reliability
Process Reliability
Maintenance Program Reliability
Types of Reliability (4 types)
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Statistical Reliability
Historical Reliability
Event-oriented Reliability
Dispatch Reliability
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Reliability
Event-oriented Reliability
 Concerned with one-time events such as bird strikes, hard
landing, in-flight shutdowns, or others accidents or incidents,
which these are events that do not occur on a regular basis.
 Each occurrence must be investigated to determine the cause
and to prevent or reduce the possibility of recurrence of the
problem.
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Reliability
Dispatch Reliability (DR)
 DR is a measure of the overall effectiveness of the airline
operation with respect on-time departure. It is a simple
calculation based on 100 flights.
 DR involves more than just maintenance
 Dispatch delays should look at the whole operation.
 On-time departure means that the aircraft has been “pushed
back” from the gate within 15 minutes of the scheduled
departure time
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Reliability
Dispatch reliability
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Reliability
Reliability Department
 Responsibility of monitoring failure rates, removals of A/C
systems and components to measure the effectiveness of the
overall maintenance program
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Data Collection
Preliminary Investigation
Issue Alert Notices
Monitor Results
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Reliability
Reliability Program
 A set of rules and practices for managing and controlling a
maintenance program
 Monitor the performance of the vehicles and their associated
equipment and call attention to any need for corrective action
 Monitor the effectiveness of corrective actions
 Provide data to justify adjusting the maintenance intervals
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Reliability
Elements of a Reliability Program
 Data collection
 Problem area alerting
 Data Display
 Data analysis
 Corrective actions
 Follow-up analysis
 Monthly report
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Reliability
Data collection
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Flight time and cycle
Cancellations and delay over 15 minutes
Unscheduled component removals
Unscheduled engine removals
In-flight shutdowns of engines (IFSD)
Pilot reports or logbooks
Cabin logbook
Component failure (shop)
Maintenance check package findings
Critical failures
▪ Data collection ▪ Problem area alerting ▪ Data Display ▪ Data analysis
▪ Corrective actions ▪ Follow-up analysis ▪ Monthly report
Reliability
Problem area alerting
 An alerting system
 Identify those areas where the performance is significantly
different from the normal
 Alert level is based on a statistical analysis
 Alert level is set at one to three standard deviations above the
mean rate
 Alert level is referred as UCL (Upper Control Limit)
 Additional calculation that can be made to smooth the curve (3
months average) and help eliminate “false alerts”
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▪ Data collection ▪ Problem area alerting ▪ Data Display ▪ Data analysis
▪ Corrective actions ▪ Follow-up analysis ▪ Monthly report
Reliability
Problem area alerting (cond.)
 Setting and adjusting alert levels
 Recommended that alert levels be recalculated yearly
UCL (Upper Control Level)
3 months
Offset
Control Chart
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▪ Data collection ▪ Problem area alerting ▪ Data Display ▪ Data analysis
▪ Corrective actions ▪ Follow-up analysis ▪ Monthly report
Reliability
Data analysis
 Reliability Department
 a preliminary analysis to determine if the alert is valid
 If valid, on-alert condition is sent to engineering for a more
detailed analysis
 Engineering Department
 Troubleshoot the problem
 Issue EO (Engineering Order)
 Recommendations to the Airline Maintenance Program Review
Board (MPRB)
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▪ Data collection ▪ Problem area alerting ▪ Data Display ▪ Data analysis
▪ Corrective actions ▪ Follow-up analysis ▪ Monthly report
Reliability
Corrective actions
 Modifications of equipment
 Correction to line, hangar or shop processes or practices
 Disposal or defective parts
 Training of mechanics
 Addition of maintenance tasks to the program
 Decreased in maintenance intervals
Completion of the corrective action is noted in the monthly
reliability report
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▪ Data collection ▪ Problem area alerting ▪ Data Display ▪ Data analysis
▪ Corrective actions ▪ Follow-up analysis ▪ Monthly report
Reliability
Follow-up analysis
 Verify the corrective action taken was indeed effective
 Reflected in decreased event rates
 If no significant change, corrective action should be reanalyzed
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▪ Data collection ▪ Problem area alerting ▪ Data Display ▪ Data analysis
▪ Corrective actions ▪ Follow-up analysis ▪ Monthly report
Reliability
Monthly report
 Working tool for maintenance management
 Picture of what problems are encountered
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▪ Data collection ▪ Problem area alerting ▪ Data Display ▪ Data analysis
▪ Corrective actions ▪ Follow-up analysis ▪ Monthly report
Reliability
Reliability Program Document
Every aspect of the reliability must be documented in an official
document signed be MPRB chairman and approved be the
regulatory authority
Include:
 Detailed discussion
 Methods used to determine alert levels
 Rules relative to changing
 Define MPRB activities and Responsibility
 Monthly Report Format
Submitted to FAA for approval
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▪ Data collection ▪ Problem area alerting ▪ Data Display ▪ Data analysis
▪ Corrective actions ▪ Follow-up analysis ▪ Monthly report
Safety
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Apr-15
Traditional Safety Management
 Loss Control - Correction approach
 Loss control is the tools for
- Prevention
- Reduction
- Elimination
 Cause of incident and accident is
-Unsafe Action
-Unsafe Condition
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Apr-15
Loss Causation Model
1. Loss
- Loss of Direct cost
- Loss of Indirect cost
2. Incident
3. Immediate Cause
- Low standard action and Low standard condition
4. Basic Cause
- Personal Factor and Job Factor
5. Lack of Control
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Apr-15
Loss Control Management Process
1.
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5.
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Identification of Work
Set Standard
Measurement
Evaluation
Commendation and Correction
Apr-15
Modern Loss Management
1. Source of Loss
- People
- Equipment
- Material
- Enviroment
2. Loss Control systems
- International Safety Rating System (ISRS) -US
- Total Loss Control Management-UK
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Apr-15
Modern Safety Management
 Modern Safety Management – Prevention, Risk Assessment
and Risk control approaches
 Modern Safety Management is Loss Control Management
 Modern Safety Management used POLC framework
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Apr-15
Modern Safety Management
 There are 4 approach to Modern Safety Management
 1. Management concept
 2. Management information system
 3. Performance standard
 4. Measurement and Evaluation system
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Apr-15
System Safety
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Apr-15
FAA - Safety Risk Matrix
FAA Advisory Circular No. 120-92, Introduction of Safety Management
Systems for Air Operators
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Apr-15
FAA - Safety Risk Matrix
 Unacceptable (Red). Where combinations of severity and likelihood cause risk to fall
into the red area, the risk would be assessed as unacceptable and further work would be
required to design an intervention to eliminate that associated hazard or to control the
factors that lead to higher risk likelihood or severity.
 Acceptable (Green). Where the assessed risk falls into the green area, it may be
accepted without further action. The objective in risk management should always be to
reduce risk to as low as practicable regardless of whether or not the assessment shows
that it can be accepted as is. This is a fundamental principle of continuous improvement.
 Acceptable with Mitigation (Yellow). Where the risk assessment falls into the
yellow area, the risk may be accepted under defined conditions of mitigation. An
example of this situation would be an assessment of the impact of a non-operational
aircraft component for inclusion on a (MEL). Defining an Operational (“O”) or
Maintenance (“M”) procedure in the MEL would constitute a mitigating action that could
make an otherwise unacceptable risk acceptable, as long as the defined procedure was
implemented. These situations may also require continued special emphasis in the safety
assurance function
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Apr-15
General Safety Rules
 Fire prevention & protection
 Hangar deluge systems
 Fall prevention and Protection
 Storage and handling
 Smoking regulation
 Hangar safety
 Shop safety
 Line safety
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Apr-15
Hand Signal
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Apr-15
Safety Management System
 ICAO has established a framework for an SMS that
incorporates four basic components and 12 elements as
shown here:
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Apr-15
MEDA Corrective Actions
THE END